Wow! Thanks so much THeff!! Xnor and I also have foniks eagle files, and some proto boards already fabbed that we will mod. Our intention was to do a run for electro-music and muff members who would be interested in a single voice PCB. It would be based on foniks layout, but with these fixed applied, and likely a little smaller. But I don't wanna step on anyone's toes here.

Xpmtl are you planning on doing a group run? If so we'll just build for ourselves so as not to have 2 similar boards on offer from different forum members.

Looking at the eagle schematic I don't think you want D1 on the input because it wants a negative going trigger. If you look at the original schematic it shows a positive spike on the cathode of D1. Since IC1a is an inverter a negative going trigger would be needed to create this. You Probably can bypass IC1a and apply a +10V trigger directly to the anode of D1 (original D1 designation), but I have not tried it.

I'm not sure what the signal output looks like from a Simmons drum sensor, but it must be a pretty high level. They have a large attenuator (68 ohms & two 150k resistors) on the input of IC1a. I fed a -5V trigger into resistor R6 (150k) without the 68 ohm and that worked fine. You will probably want to play with this values to match your trigger source.

I just lifted pin1 on IC1a and applied a positive going 5V 1mS pulse to the anode of D1 (original D1 designation). This works just fine. So, the IC1a inverter is not really needed unless you have negative going triggers.

This is really great - thanks guys! So pumped to finally get this thing on track! We'll make the same changes to our prototypes and get this going! As soon as we have a corrected board printed and working we'll do a big community run!

The noise feedthrough mod looks correct they way you have it drawn and that's the way I have it connected.

I built the noise circuit just the way it is drawn using the LM301 and 2N5172 transistor and it doesn't sound very good to me. I tried the gimmick capacitor (twisted wires) and then replaced it with a 1-2 pF cap with the same results. A small change in capacitance here makes a big difference in the frequency roll-off.

The noise has a crackling clipping sound instead of smooth white noise. I'm sure this will vary depending on the transistor that you use but I think adopting some of the other noise circuits out there might be more predictable and sound better for snares or cymbals.

1.) Concentrate on the filter/osc since it is the heart of the drum. It runs all the time and you should see a 9V p/p sinewave on PIN 1 of IC3a when it is working correctly. The trigger only opens the VCA and activates the Bend modulation.

2.) Don't worry about the trigger, noise, or LFO till you get the filter working.

Here are the DC voltages for all of the pins on IC4, IC5, and IC6 (CA3086) with the following conditions:

All panel control pots full counter clockwise except the pitch control. Set the pitch control so that you have about -7.78V on the wiper. This sets the pitch on my board to about 500Hz. LFO=OFF, BEND=Down.

This is really great - thanks guys! So pumped to finally get this thing on track! We'll make the same changes to our prototypes and get this going! As soon as we have a corrected board printed and working we'll do a big community run!

Yep - on monday we're going to get back to troubleshooting this guy. Working from the same schematic as xpmtl - the one inherited from Fonik, and pasted on the previous page here. LFO is included (And also the only functional part of our prototype atm) - I'm actually unclear on what the 'Run Generator' is.. can someone explain?

The Run Generator is simply a staircase waveform applied to the filter/osc CV so that each time you trigger the drum it steps the pitch down. I played with it a little bit and it's kind of tricky to get the timing right.

xpmtl,

Are you sure you have the FETs installed correctly? It sound like you have a large DC offset on IC3.

I noticed that I gave the wrong information about connecting pins 2 & 3 of IC3a. I said that pins 2 & 3 of IC3a are swapped and I should have said that Resistors R50 & R51 are swapped. Listing out the junctions of these parts caused further errors and confusion.

Only had an hour to fiddle with it yesterday but i made some progress.

I got most of the functions working and got sound now...

BUT

- Pitch pot doesn't work, only a small spot on the pot actually does something. It's not sweeping, more like when you turn the knob, it's silent then at one point it passes signal then silent again. i checked if the pot was busted but it's fine actually.
- Filter still buggy
- Noise doesn't work

I need to disable the LFO as i think it's what i'm hearing at the output (didn't use a switch for that). That will allow me to concentrate on the vcf as even if i see the sine wave, i got the impression it doesn't reach the output.

Need to look more into all that, i'll do that this week.

More later

EDIT : Noise works now, there's an error in Matthias schematic, Cap C15 is not at the right place._________________http://sdiy.xpmtl.net

Decay has some effect over 2 frequencies, one high frequency, and one lower. We added a pitch pot per Michael B's recommendation (will attach a drawing later), but neither it, nor the global pitch pot have any effect on the oscillations.

We encorporated all the fixes mentioned by THeff (except for led orienation - because they seem to be working correctly), and we also fixed the resistor location on the lfo that xpmtl mentioned. (We moved the resistor - not the cap - but I'm sure it's the same fix.)

The lfo runs, but sounds mixed with the main output - it doesn't modulate the ringing tones. The 2 tones ring for a very long time - and decay does have some control over them - but we are using a linear pot and haven't swapped it out with a log yet. The only other pots that are working are LFO rate, and GAIN. The lfo switches work as well.

We didn't change the trigger input at all - it is triggering on falling edge.

We measured pin voltages - everything looks pretty close to THeff's list (except IC4 is kind of all over the place).

We do get a sine wave on IC3, but it is less than a volt peak to peak. This is the high frequency we are hearing. The low frequency sounds almost like ground hum - but it effected by the decay.

Noise is doing nothing, but we may have the twisted wire thing wrong, haven't done that before. Just 2 disconnected twisted, jacketed wires or what?

NOTE: we don't have the run generator on this board (it's pretty much the schematic xpmtl posted)

Any thoughts/ideas? We are going to re-draw the schematic with these applied changes... but clearly there is still more to fix!

I'm in the process of redrawing everything based on the original schematic with the same references as the original as advised by Tim.

It's kind of a long process as I have to change the value of each components manually. Should have finished this weekend if time permits.

jmejia, noise circuit should work if you change the capacitor placement, compare with the original schematic. The twisted wires only change the quality of noise.

For me Decay works but it is too long even at minimum value. I'm sure the resistor in series with the pot is too big on my board (haven't changed it yet).

Bend pot also does something, it adds a kind of delay between impact and the output.

Up/down switch doesn't do much.

Impact pot works.

LFO works tho triangle wave is a bit shy.

If you can post your pitch circuit it would be great. I was asking myself why the original schematic only have the overall pitch pot. On the SDS3 there's an individual pitch pot that i couldn't locate...

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